Dissecting the oncogenic role of EP300 in LSC. (A,B) Representative scatter plots showing MLLr leukemia relative dependency on EP300 (A) and CREBBP (B) with n = 7 MLLr leukemia cell lines compared with n = 25 non-MLLr leukemia cell lines and n = 593 nonleukemia cancer cell lines. Y-axis shows the dependency rank of EP300 or CREBBP in an individual cell line. X-axis shows the dependency score in each cell line. (C,D) Protein levels of EP300 (C) and CREBBP (D) in LSCs, expressing corresponding shRNAs against the 2 HATs. (E) Immunoblots of H3K27ac in LSCs after knockdown of control, Ep300 and Crebbp (n = 3; mean ± SD). (F) Morphology and quantification of colonies of Ep300 and Crebbp knockdown cells (n = 3; mean ± SD). Scale bar, 20 μm. (G) Bar graph indicates LSC enhancer–associated gene transcript levels (Hoxa1, Id2, Mpo, and Spry2) in cells transduced with the indicated shRNAs. Transcript levels were quantified by RT-PCR and expressed relative to control vector (n = 3; mean ± SD). (H) ChIP-qPCR of H3K27ac at enhancers in LSCs upon loss of EP300 and CREBBP. IgG enrichment was used as a negative control (n = 3; mean ± SD). ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. ns, not significant; RT-PCR, reverse-transcriptase PCR.